The goal of this proposal is to understand the neural mechanisms underlying communication and social behavior and related emotional and motivational states, particularly individual and kin recognition. A related goal of is to understand the neural mechanisms underlying these processes, especially the discovery of areas of the brain involved in social recognition and memory, emotional and motivational mechanisms related to recognition of familiar individuals and the consequent social behavior, and the sensory processes related to these abilities. The results will be relevant to understanding many types of mental and behavioral disorders that involve social interactions, such as autism and depression, personality disorders (e.g., antisocial, avoidant, paranoid or schizoid), social anxiety, social phobias and the effects of socially induced stress and post-traumatic stress. In addition, the findings will be relevant to disabilities due to stroke, head injury, or degenerative diseases, including Alzheimer's disease. The specific aims of the study are to use our extensive knowledge about social behavior and communication in hamsters as a model system to investigate the neural mechanisms of recognition of individuals, kin, and sex by odors. There are three specific goals. (1) Using immunohistochemistry to identify cells expressing immediate early genes, we will identify brain areas activated during response to familiar individuals and appropriate emotional responses to them. (2) Using micro-infusion of lidocaine, we will determine which brain regions are necessary for individual and sex recognition and appropriate responses to such individuals. Brain areas of particular interest include the olfactory projection pathways, basolateral and medial amygdala, entorhinal cortex, peri-rhinal cortex, the hippocampus, and the subiculum. (3) The role of the main and accessory olfactory bulbs in processing information about individuals and kin and the role of social experiences in altering the patterns of activity in the bulb. These experiments will provide new and unique knowledge about the neural basis of social recognition, social memory, and the emotional and motivational responses caused by interactions with known individuals. These mechanisms are essential building blocks in the social behavior of non-human animals and humans.